This invention relates, in general, to tools and equipment for completing a subterranean well that traverses a hydrocarbon bearing formation and, in particular, to a retrievable well packer for releasably sealing the annulus between a tubing string and the well casing using a collet member to positively operate a support ring.
In the course of treating and preparing a subterranean well for production, a well packer is run into the well on a conveyance such as a work string, a production tubing, a wireline or the like. The purpose of the packer is to support production tubing and other completion equipment, such as a sand control screen adjacent to a producing formation, and to seal the annulus between the outside of the production tubing and the inside of the well casing to block movement of fluids through the annulus past the packer location.
Typically, the packer is provided with an upper and a lower set of anchor slips having opposed camming surfaces which cooperate with complementary opposed wedging surfaces, whereby the anchor slips are outwardly radially extendable into gripping engagement against the well casing bore in response to relative axial movement of the wedging surfaces. The packer also carries annular seal elements which are expandable radially into sealing engagement against the bore of the well casing in response to axial compression forces. The longitudinal movement of the packer components which set the anchor slips and the sealing elements may be produced, for example, hydraulically or mechanically.
After the packer has been set within the well casing, it should maintain its sealing and griping engagement upon removal of the hydraulic or mechanical setting force. Additionally, it is essential that the packer remain locked in its set configuration while withstanding hydraulic pressures applied externally or internally from the formation and/or manipulation of the tubing string and service tools without unsetting the packer or interrupting the seal. This is made more difficult in deep wells in which the packer and its components are subjected to high downhole temperatures and high downhole pressures.
Moreover, the packer should be able to withstand variation of externally applied hydraulic pressures at levels such as 10,000 psi in both directions, and still be retrievable after such exposure for long periods of time such as 10 to 15 years or more. After such long periods of extended service under extreme pressure and temperature conditions, it is desirable that the packer be retrievable from the well by appropriate manipulation of the tubing string, such as a quarter turn of rotation, to cause the packer to be released and unsealed from the well casing, with the anchor slips and seal elements being retracted sufficiently to avoid becoming stuck within wellbore restrictions.
It has been found, however, that in certain packer deployments, the deviation of the wellbore may cause the packer to rest on the inside of the well casing. In these deployments, it is difficult to properly set the upper anchor slips due to a lack of cooperation of the opposed camming surfaces of the upper anchor slips with the complementary opposed wedging surfaces as the force of gravity cannot fully act on the support ring. Therefore, a need has arisen for a retrievable packer that is capable of being properly deployed in a well wherein the packer rests on the inside of the well casing. A need has also arisen for such a retrievable packer that is capable of withstanding the extreme downhole pressures and temperatures without unsetting the packer or interrupting the seal. Further, a need has arisen for such a retrievable packer that is capable of being set, unset and reset in the well casing and remaining in the well for long periods of extended service then be retrieved from the well.
The present invention disclosed herein comprises a retrievable packer that is capable of being properly deployed in a well wherein the packer rests on the inside of the well casing. The retrievable packer of the present invention is also capable of withstanding the extreme downhole pressures and temperatures without unsetting the packer or interrupting the seal. In addition, the retrievable packer of the present invention is capable of being set, unset and reset in the well casing and remaining in the well for long periods of extended service and later being retrieved from the well.
The retrievable packer of the present invention comprises a packer mandrel that is adapted for connection to a tubing string. A seal assembly is disposed about the packer mandrel. The seal assembly has a running position, wherein the seal assembly is not in sealing engagement with the well casing, and a sealing position, wherein the seal assembly is in sealing engagement with the well casing. A first slip wedge is slidably disposed about the packer mandrel. The first slip wedge is operably associated with the slip assembly and may include plurality of wedge sections.
The retrievable packer of the present invention also includes a support ring that is slidably disposed about the packer mandrel. The support ring is operably positionable at least partially between the first slip wedge and the packer mandrel to prevent radially inward travel of the first slip wedge and to apply an axial force on the first slip wedge to operate the seal assembly from the running position to the sealing position. A slip assembly is slidably disposed about the support ring. The slip assembly is operably associated with the first slip wedge and has a running position, wherein the slip assembly is not in gripping engagement with the well casing, and a gripping position, wherein the slip assembly is radially outwardly extended by contact with the first slip wedge into gripping engagement with the well casing.
In addition, the retrievable packer of the present invention includes a collet member that is slidably disposed about the packer mandrel. The collet member has a first operating position, wherein the collet member applies an axial force on the support ring to positively position the support ring at least partially between the first slip wedge and the packer mandrel, and a second operating position, wherein the collet member applies an axial force on the slip assembly to operate the slip assembly from the running position to the gripping position.
The seal assembly of the retrievable packer of the present invention may include a mandrel element slidably disposed about the packer mandrel, a second slip wedge slidably disposed about the mandrel element and at least one seal element disposed about the mandrel element such that a compressive force between the mandrel element and the second slip wedge radially expands the seal element. Likewise, the slip assembly of the retrievable packer of the present invention may include a slip carrier and a plurality of slips that are radially outwardly extendable, by contact with the first slip wedge, into gripping engagement with the well casing.
The collet member may include a plurality of collet fingers that are radially retracted when the collet member is in the first operating position and radially expanded when the collet member is in the second operating position. In addition, the collet member may comprise a spring cover.
It should be noted that the retrievable packer of the present invention may be set, unset and reset any number of times. Specifically, the seal assembly of the retrievable packer of the present invention can be repetitively operated between its running position and its sealing position without removing the packer from the well casing. Likewise, the slip assembly of the retrievable packer of the present invention can be repetitively operated between its running position and its gripping position without removing the packer from the well casing.
In another aspect, the present invention comprises a method of setting a retrievable packer to establish a sealing and gripping engagement with a well casing. This method includes lowering the packer into the well casing to a selected location, axially shifting a packer mandrel within the packer, positively positioning a support ring at least partially between a first slip wedge and the packer mandrel by applying an axial force on the support ring with a collet member, operating a seal assembly from a running position wherein the seal assembly is not in sealing engagement with the well casing to a sealing position wherein the seal assembly is in sealing engagement with the well casing, repositioning the collet member to apply the axial force on a slip assembly and operating the slip assembly from a running position wherein the slip assembly is not in gripping engagement with the well casing to a gripping position wherein the slip assembly is radially outwardly extended by contact with the first slip wedge into gripping engagement with the well casing.